2016 F350 ....6.7 diesel dually......Bought new......35,000 miles, no problems, been a great truck......Only the stock fuel tank, no saddle tank etc.....

Got home from a 3500 mile trip 2 weeks ago and the tank was about 1/8 full, I had last filled up in Kingman AZ, no issues....Pulled into a gas station in San Diego to fill up.....Opened the gas cap and a quart or so of diesel spit out the filler tube....Wiped down my arm etc and the tank took about 2 gals and diesel was right to the top of the filler tube...I watched it for 10 mins and it did not go down.....I could see the fuel at the top of the filler tube....I know the tank was almost empty, gas gauge also showed about 1/8......Put the cap back on and drove home, ran just fine.....

Drove home, unloaded the camper and a few days later returned to a different gas station..Took about 2 gals, same thing happened.....Few days later filled up a 5 gal can and attempted to SLOWLY empty the can..Took less than a gallon, fuel right to the top of the filler tube.....Watched it for a full hour, it did not go down..... Drove it for about 50 miles then, all was fine...Truck drives like it always has--just fine....I know the tank is about 1/8 full due to the miles from Kingman to San Diego....In a locked barn, etc so nobody has access.....Fuel gauge shows also 1/8.....

Opinions?? I have never run into this before......I have crawled underneath and the fill hose looks straight, no kinks.....I can reach along the hose to the top of the tank and it feels fine......Called the dealer where I bought it and of course bring it in and they will look at it....I try to do my own maint so inquiring for assist here......

 

Sounds like you have a liquid blockage in the tank vent line. Vent line is the smaller hose the runs from tank to fuel filler. Make sure there is no low spots or kinks in the line.

 

If it were the vent line, why would the fuel in the filler neck not gradually go down? Would it be possible to thread a soft hose down the filler neck into the tank? That would provide a temporary second vent line and would also indicate whether the full tube was somehow blocked. Just at thought.

Steve

 

You said you checked the fill hose, but the problem would have to be the vent side that is next to the fill line.
Now I am not home to look at mine right now, but there has to be a kink or something blocking the vent line as if you don't let the air out you cannot put anything in.
Did you by chance just put some type of additive in your fuel just before this happened and lost the cap seal?

 

I think the reality is not one of us has a clue what is going on here because the problem is so unusual. I would not rule out any possibility and approach this task first as a fact finding mission. I think you will find even with a completely blocked breather tube it is normally still possible to trickle fuel into the tank, so is the filler tube somehow blocked or kinked?

Steve

 

Pulling ideas out of my back side here...is there a return line from engine to the tank that is near or in the filler neck? That's the only way I can see the fuel developing some pressure in the filler neck (enough to spray you in the arm). And the filler neck would have to be blocked (as mentioned).

Does this truck have an electric lift pump in or near the fuel tank?

 

OP here...I also thought the vent tube as the issue..But---when I filled it with a gas can I filled it really REALLY slowly..Small "nozzle" on the gas can.... I would have thought it would vent out the filler tube itself with such a small nozzle putting the fuel in and going slowly.......Yesterday I crawled underneath again....Vent and filler tubes look good, no visible kinks, etc......I also thought someone might have stuffed a rag or something into the filler tube, so I tried it again yesterday, got only about 2 qts in and filled to the top.....Let it sit for an hour, still at the top.....Then an hour after that checked and it had drained into the tank....So I am at a loss.........

I talked to a good independent diesel shop in Temecula (CA) and going to take it in tomorrow.....I will post what the results are......Thx for the input so far.....

 

While that filler tube is full, put the cap on and squeeze the rubber part of the filler tube under the truck and that could unblock the vent tube possibly.
Well, just thinking anyway as that would slightly pressurize the fill tube. :-)